Association of American Railroads
The Association of American Railroads (AAR) is an industry trade group representing primarily the major freight railroads of North America. Amtrak and some regional commuter railroads are also members. Smaller freight railroads are typically represented by the American Short Line and Regional Railroad Association (ASLRRA), although some smaller railroads and railroad holding companies are also members of the AAR. The AAR also has two associate programs, and most associates are suppliers to the railroad industry.
Association of American Railroads WWII poster
Multiple-unit train control
Multiple-unit train control, sometimes abbreviated to multiple-unit or MU, is a method of simultaneously controlling all the traction equipment in a train from a single location—whether it is a multiple unit comprising a number of self-powered passenger cars or a set of locomotives—with only a control signal transmitted to each unit. This contrasts with arrangements where electric motors in different units are connected directly to the power supply switched by a single control mechanism, thus requiring the full traction power to be transmitted through the train.
Two ICE 2 trains operating in multiple-unit train control in Bielefeld, Germany
South Side Elevated Railroad car #1, one of the cars that Frank Sprague converted to MU operation in Chicago
Two Japanese Shinkansen trains operating in multiple-unit train control
Two ZiU-9 trolleybuses operating in multiple-unit control in Leningrad, USSR